Field of the Invention
The present invention relates to a vibration wave motor including a vibrator and a friction member in frictional contact with the vibrator, wherein the vibrator and the friction member are displaced relative to each other.
Description of the Related Art
Conventionally, various proposals are made in relation to an ultrasonic motor that generates an elliptic motion at a predetermined place of a vibrator to relatively move the vibrator and a friction member in frictional contact with the vibrator and in relation to an imaging apparatus including the ultrasonic motor as a driving source of a mechanism unit and a lens of a camera. The ultrasonic motor is disclosed in Japanese Patent Application Laid-Open No. 2013-158151. The vibrator included in the ultrasonic motor includes a piezoelectric element, and AC voltages of two different phases can be applied to the piezoelectric element. The voltages are applied to the piezoelectric element to excite an elliptic vibration wave in a projection and the like provided on a surface of the vibrator. The projection of the vibrator is brought into contact with a friction member by pressure to generate driving force, and the vibrator slides on the surface of the friction member at desired driving force. The vibrator is provided with a support portion (connection portion) and includes a holding member for holding and fixing the vibrator at the support portion. A vibrator including a piezoelectric element is disclosed in Japanese Patent Application Laid-Open No. 2011-254587 for example. Vibration displacement of an extending portion of the vibrator is greater than that of a fixing portion, and vibrational energy is stored in the extending portion. Concentration of the vibrational energy on the fixing portion is avoided.
When the holding portion of the vibrator is held and fixed by the holding member, a holding structure for preventing inhibition of the vibration of the vibrator is necessary in order to efficiently generate desired elliptic motion in the projection and the like of the vibrator. More specifically, when the elliptic motion is generated at a desired place, the vibration is not generated in the holding portion of the vibrator, but the vibration is generated around the holding portion. Therefore, it is important to design a holding structure that reduces the vibration in the holding portion of the vibrator as much as possible. However, if an abutting range of the holding member and the holding portion of the vibrator is enlarged to surely hold the vibrator, the vibration of the vibrator is inhibited. The desired elliptic motion is not generated in the vibrator, and a malfunction occurs in the ultrasonic motor. The conventional technique has a problem that the abutting range of the holding member and the holding portion of the vibrator is not specified, and the vibration of the vibrator is inhibited.